The Vaginal Infections and Prematurity (VIP) Study, jointly sponsored by NICHD and NIAID, is a prospective study designed to investigate the relationship between genital tract colonization with various microorganisms and the subsequent development of preterm birth. It also incorporates a clinical trial of erythromycin to prevent preterm birth among women colonized with Ureaplasma urealyticum, Chlamydia trachomatis, and group B streptococcus. In addition, the VIP collected a wealth of additional data on a variety of factors possibly linked to pregnancy outcome. This project will analyze these factors. Analyses undertaken to date include the predictive value of vaginal Gram stain in the identification of group B streptococcus, the descriptive epidemiology of group B streptococcal carriage, the relationship between reported physical activity and preterm birth, the effect of treatment with erythromycin on pregnancy outcome among women colonized with group B streptococci, and the association between sexual intercourse during pregnancy and preterm birth among colonized with different genital microorganisms. Questions under analysis include the effect of group B streptococcal colonization on pregnancy outcome, the association between bacterial vaginosis and pregnancy outcome, and the effect of treatment with erythromycin on pregnancy outcome among women colonized with Chlamydia trachomatis.